Combustible core for forming ducts in concrete structures



March 1952 w. F. WILHELM ET AL 2,589,177

COMBUSTIBLE CORE FOR FORMING DUCTS IN CONCRETE STRUCTURES Filed March 27, 1948 2 SHEETS-SHEET 1 /Z- Q I 1 v I W 1 m b t 1 b v bl INVENTOR WqznzarfifiZ/z m, BvWcLrrerzfWdmZm,

March 11, 1952 w. F. WILHELM ET AL COMBUSTIBLE CORE FOR FORMING DUCTS IN CONCRETE STRUCTURES Filed March 27, 1948 2 SHEETS SHEET 2 v0 5 0 6 o a a v o the like.

Patented Mar. 11, 1952 COMBUSTIBLE CORE FOR FORMING DUCTS IN CONCRETE STRUCTURES Warner F. Wilhelm and Warren F. Wilhelm, Chicago, 111.; said Warren F. Wilhelm assignor to Cora M. Wilhelm, Chicago, Ill.

Application March 27, 1948, Serial No. 17,456

In our co-pending application, Serial Number 555,415, filed September 23, 1944, now Patent No.

2,438,528 of which the present application is in part a continuation, we have described and claimed methods and means for the draining of excess water from plastic cement, concrete and We have found that by suitable modification of the invention described and claimed in the aforementioned parent application, it is possible to produce shaped passageways in cement, concrete and similar structures, accompanied or not, as desired, by the drainage of excess water from said structures while in plastic condition. These passageways are adaptable to many uses. For example, they may serve as conduits for electric Wire or cable, as pipes for the transportation of liquids or gases, as points of attachment for various structures exterior to the cement or concrete, et cetera.

It is an object of this invention to provide means for the formation of shaped passageways in cement, concrete and similar structures.

A further object of this invention is to provide means for facilitating the drainage of excess water from plastic cement, concrete or similar structures and the formation of shaped passageways in said structures.

Additional objects of this invention will become apparent as the description thereof proceeds.

For the better understanding of this invention, reference may be had to the accompanying sheets of drawings, wherein: 7

Figures 1 to 5 are cross sectional views of several modifications of one form of device suitable for accomplishing the objects of this invention;

Figures 6 and 7 are cross sectional views of modifications of another form of device suitable for accomplishing the objects of this invention;

Figure 8 is a cross sectional view of a third form of device suitable for accomplishing the objects 1 this invention; and

Figures 9 to 16 are'isometric views of several suitable methods of employing the devices of Figures 1 to 8 for accomplishing the objects of this invention.

Turning now to a more detailed description of Figure 1, reference character I designates a general cross sectional view of a device suitable for accomplishing the objects of this' invention, consisting of a relatively or completelywater ime pervious layer or sheath 2. and a core 3 capable of self-sustained combustion in the absence of air. One mode of application of the device of Figure 1 for accomplishing the objects of this invention is shown generally in Figures 9 and-.10.

4 Claims. (Cl. 25-428) In Figure 9, the end closure of a cement or concrete form is designated by Ill, while the side closures of said form are designated l I. End closure In is provided with an opening I 2 through which a free end of the device of Figure 1 extends. The form is filled with plastic cement or concrete to the approximate level indicated by I3 and the device of Figure 1 is laid along the surface thereof following which additional plastic cement or concrete is added to the form to the level desired for the particular structure being made. Figure 10 is exemplary of a portion of a completed cement or concrete structure with the form removed andwith the device of Figure 1 extending therethrough. The water impervious sheath 2 (Figure 1) obviously protects the core 3 (Figure 1) from deterioration. On ignition of the core 3 (Figure l) combustion proceeds throughout its length and a shaped passageway is formed in the cement or concrete, thereby accomplishing the objects of this invention.

It is not necessary that the form be partially filled with cement or concrete, the device of Figure 1 laid on the surface thereof, and the remaining cement or concrete added as above described. If desired, the device of Figure 1 may be positioned in an empty form following which the whole charge of cement or concrete is added. When proceeding in this manner, it is necessary that care be exercised to prevent dislodgment or breaking of the device of Figure l as the heavy cement or concrete is poured into the form.

Also, it is not necessary that a material of the physical characteristics of freshly preparedcement or concrete be employed. Solids of particulate form, as well as certain liquids, are equally adaptable. For example, a liquid monomer that reacts to form a solid polymer through the action of heat, catalysts or the mere passage of time is suitable. Likewise, liquids that change to solids on reduction of temperature are applicable, for example, water. Solid polymers in particulate form which are convertible to consolidated solids by the application of heat and/or pressure (injection or compression molding) can be used. Also, this invention may be applied to particulate solids such as coal, sand, soil and the like. Sand. for example, maybe poured around positioned devices of Figure lif; freezing weather is expected. When required for use, the frozen mass of sand may be thawed by ignition of the cores.

While the broad principles of the instant in= vention have been generally set forth above, many specific. modifications maybe employed without departing from the spirit or scope thereof.

The relatively or completely water impervious sheath 2 may itself be combustible or non-combustible, as desired. Preferably, this sheath is flexible to facilitate the formation of passageways with bends, curves, et cetera, as may be desired or necessary. A sheath of cellulose ace-.

tate or nitrate or a mixture of the two may be used if a combustible sheath is desired. Vinyl chloride or vinylidine chloride polymers, natural or synthetic rubber also are suitable for useas sheathing materials. However, sheaths exhibiting a satisfactory resistance to penetration by water can be prepared simply by the application. of suitable glazes, asphalt, tar or the like to woven on woven sheathsby impregnation with silicone resinsby methods now well known to, those skilledin the art.

Thecore 3 may take-a wide Varictyof forms without departing from the spirit or scope of the present invention. Once ignited, it is desired that combustionv of the core proceed; at a reasonably fast rate but, at the same time, it isnecessary that this rate at-no time approach too. great proportions. fuse satisfies these requirements under most circumstances, especially when relatively short lengths are employed: This fuse is usually'made with a burning rate of to 40 secondsper footand, the combustion of. the black powder core, which isaccompanied by combustion of a considerableproportion of the surrounding fibrous members, results intheformationof shaped pas sagewaysin the cement, concrete or similar structure, thereby, accomplishing the objects of thisinvention. Another suitable core material consists. of combustible particles such as alpha cellulose particles, part or all of which are impregnated with an oxygen supplying agent such as potassium, sodium or ammonium nitrate, chlorate or perchlorate.

Manyvariations in the structureofthecore are. possible without departing from the spirit orscope of thepresentinvention. Someof these modifications are shown in Figures 2, 3 and-4.

In- Figure 2, the device I, consisting of a, rel-i ativelyorv completely impervious-sheath 2. surrounding a core 3, is shown as before, core, 3 being madeupof a plurality of elongated fibers [capable of self-sustained combustion. These fibers may take the form of elongated strings made from cotton or similar fibrous materials.

These are impregnated witha suitable chemical for'supplying oxygen such as potassium, sodium or; ammonium nitrates, chlorates, perchlorates or-the like. 3"of--the type shown in Figure 2 may be controlled by impregnating only a certain portion of the fibers with the oxygen supplying compound. This is shown in Figure 3', in which a portion of' the fibers are impregnated with the oxygen supplying compound (these being designated 4) while the remainder of the fibers (designated Ordinaryblacle powder-- The rate of combustion of the core a.considerahle rangeaby suitably varyinggth pro 5) are not impregnated. Of course, sufiicient impregnated fibers are present to insure selfsustained combustion of the whole. Yet another modification is shown in Figure 4, in which the core 3 carries along a portion or all of the longitudinal dimension thereof a train 6 exhibiting a considerably more; rapid combustion rate than that of the core proper. On, ignition, the train 6 rapidly transmits combustion along the whole length of the train, and this ignites the contiguous portion of the slow burning core 3 in arelatively. short period of time. After ignition, the core smolders until combustion is complete and: the desired passageway has been formed.

While it is comparatively simple to fix the rateof combustion of core 3 at any desired value on the basis of experimental determinations 'made on short lengths of I in air or embedded in concrete, cement or similar structures, it has been. found that theresults of such experimental i'determinations of combustion rate are not neces- -sarily applicable to long lengths of I-embedded' in concrete, cement or similar structures.

Fre quently the. rate of-combustionof core 3 in long runs of. device I, embedded in cement, concrete orsimilar structures.isconsiderably higher than wouldbe predictedon. the basis of experiments made with short lengths of, I- We have arrived at. a, simple explanation of this phenomenon which we believe to. be accurate, but wedo not Wish. to. be bound by. any theory proposed. It

is, well. known that the rate of combustion ofblack. powder, for-example, varies directly with pressure,' In mining operations, for example, it hasJlong. beenrecognized that the burning rate of. a fuse that hasbeen. thoroughly and tightly stemmed in a. shot holei appreciably higher than that of a fuse that is not stemmed oris only. loosely stemmed. With respect-to the present,invention, it isevident that during the combustion of. core 3, ofa. long run. of I embedded in cement; concreteor a similar structure, a point, is reached where the: products of combustiolrare unableto-escape from thecombusti o n. zone as. rapidly as they areproduced due to increasing pressure drop along: the passageway being formed. As a result, thepressure at the point of. combustion rises above-normal which results in an, increase in combustion rate. Obviously, this phenomenon is auto-accelerating and in extremely long runs the combustion rate ,mayreacha very highvalue.

Wehave been successful inavoiding this autoaccelerating combustion: phenomenon in long lengths. of I, by forming, said long lengths with cores '3 of a: progressively changing rate of com bustioni For example, with the device of Figure' 1-, having a core 3 containing material of particulate form capable of self-sustained'combustion, for example, black; powder or-cellulose particles-impregnated with an oxygen supplying material,- the composition of the core is varied along its length-,being relatively richin material capable of self-sustained combustion at one-extremity andcontaining considerable dilue1 t a-t t-he; other. As is well known, the rate. of combustion of-fblackz powder;may be:- varied over portions: of the maior=components thereof, viz.,

potassium-nitrate; sulfur and carbon. The rate ers, for example, potassium chloride, in the blackpowder.- Thus; a long length of I maybe formed with a core 3 of progressively varying composition and hence combustion rate, consisting of, for example, straight black powder at one extremity and grading down to black powder admixed with considerable detardant at the other.

The similar modification of cores containing, for

example, alpha cellulose particles impregnated with a material capable of supplying oxygen should now be obvious. In such a case, the impregnated particles may be used exclusively at one extremity of the core while at the other extremity a considerable proportion of unimpregnated particles are to be found.

Similar methods may be used to control the combustion rate of long runs of devices such as are shown in Figures 2 and 3. With the device of Figure 2, for example, fibers 4 may be more strongly impregnated at one extremity of the long run than at the other. With respect to the device of Figure 3, the proportion of impregnated fibers 4 may be relativel high at one extremity of the long run and relatively low at the other.

Also, control of combustion rate may be achieved by providing devices of uniform cross sectional area as shown in the figures but provided with cores of progressively increasing cross sectional area on proceeding from one end of the run to the other. Or, the devices themselves may be made with a progressively increasing cross sectional area on passing from one extremity to the other. Additionally, a device having a uniform cross sectional area may be provided with a core having a cross sectional area varying periodically along the longitudinal dimension of the device, being of normal size for a short distance, tapering down to a mere train for a time, then expanding to normal size again, this periodic variation being continued throughout the longitudinal dimension of the device.

By the application of the above principles, a series of devices I may be provided, the devices in one series being, for example, 100 feet long and of such design as to insure combustion of a run of this length without reaching excessively high combustion rates. Other series may be provided, the members of each series being longer or shorter than the 100 feet mentioned above.

Also, it is possible to control combustion rate and avoid extremely high auto-accelerated combustion rates by purely mechanical means, involving the provision of suitable vents at spaced intervals along long runs of l. This is illustrated in Figures 11 and 12, wherein l4 designates a section of a concrete, cement or similar structure containing a portion of a long run of device I. In Figure 11, l is provided with a side member l5, reaching to the surface of the coni crete, cement or similar structure. In Figure 12, I follows a sinuous path all the particular region illustrated, reaching the surface of the.

to extremely high values is prevented. Obviously, these vents are distributed along long runs of l as necessar to accomplish the desired purpose. These vents may serve other useful purposes, for example, as outlets for electric wire or cable to be carried by the shaped passagcway proper.

If desired, device I may be provided with a suitable fish Wire to facilitate the pulling through of electric wire or cable after the shaped passageway has been made as previously described. In Figure 5, a suitable fish wire 1 is shown within device I. Fish wires are commonly made of iron or steel. In the present application, the fish wire is exposed to strong oxidizing conditions at elevated temperatures during the combustion process which may considerably weaken or even destroy an ordinary iron or steel wire. Accordingly, it is well here to coat such wires with a protective layer of a ceramic glaze or use wires more resistant to oxidizing conditions such as stainless steel or Nichrome (nickel-chromium alloy) wires.

By suitable modification, the devices of Figures 1 to 5 may be made to serve the dual purpose of draining excess Water from plastic cement or concrete following which shaped passageways are formed therein as previously described.

As is well known, cement and plaster of Paris, to cite but two examples, are materials classified as hydraulic cements. That is, the set of these materials is due in large measure to chemical union of one or more components of the cement with water. The subsequent interlocking of the resulting hydrated crystals accounts in large measure for the strength exhibited after setting. Accordingly, hydraulic cements require a definite quantity of water in order to set properly and develop maximum strength. On the other hand, as a rule, mixtures of hydraulic cements and water usually require much more water than necessary for chemical reaction in order to produce a mix of sufficient plasticity to be handled easily. Once this plastic mass has been placed as desired, for example, in suitable forms, this water in excess of chemical requirements is no longer needed and, in fact, should be removed as completely as possible before proceeding further. By suitable modification, the devices of Figures 1 to 5 may be used to drain this excess water from the plastic cement or concrete following which shaped passageways may be produced as previously described.

Figure 6 is a general cross sectional view of a device suitable for accomplishing the two objects just outlined. In this figure, reference character 2 represents a relatively or completely water impervious layer or sheath which may be combustible or non-combustible, as desired, while 3 is a core capable of self-sustained combustion in the absence of air. Reference character 8 designates a drain member comprising a peripheral layer or sheath of absorptive material such as fibrous cellulose, rock wool, fiber glass and the like. The Whole is surrounded by the freshly poured cement or concrete, as previously described. Excess water enters the peripheral sheath through capillary action and the like and drains from the exposed ends of the device, all as has been explained in detail in our co- .pending application previously referred to.

Obviously, any of the devices of Figures 1 to 5 or any modification thereof may be provided with a drain member comprising a peripheral layer or sheath 8 of absorptive material for the accomplishment of the ends previously set forth.

If desired, the peripheral drain member 8, after discharging its primary function of removing excess water from the plastic cement or concrete, may then contribute to the subsequent formation of shaped passageways in-the resulting structure. ,If the completely or relatively water impervious sheath 2 is combustible, part rrall ofthedrain; member 8 will be consumed dur ng; he urn: out.v operation. assuming, of. co rse,-. that... drain member 8 is;made from. combustible material, for; example cellulose fibers. The'combustionof drain member; 8 may be facilitatedby. incorporating therein a plurality of. cores capable of self-sustained combustion in the absence. of air; Such a.device. is shownin Figurefl. Here theperipheral drain member -il carries, a plurality of-inserts 9, eachconsisting oi a relatively or completely water impervious sheath 2Asurroundinga core 3A capableof selfsustained'combustion in the absence of :air. The,

device of Figure '7, after exercising its; drainage function, is;allowed to dry out partially or completely; following which it-is; ignited, to form a:

of potassium, sodium or. ammonium. nitrate,

Member 9 may beimpregnated withsuch a;s olutionby placing the; free end-or endsof 9fingsald' solution whereby the desired chemical isdrawn.

into 9 by-capillary action, Or, thesolutionmay be-pumped into 9 onmay be; added; to 8;by' othcrx suitable1means; forexample, through the ventsshown in Figures; 1 1 and. 1 2. Afton removal. of most or all. off the; solvent, 9 may be ignited as usual to; produce shaped; passageways; in; the structure...

D vices withperinheral' drain-m mbers 8 may be -.used,..if, occasiondemands, to add-water to cement or conc fiteto, promote the curing there: 7

of. For example, after; excesswater has;been

drainedfrom the hydraulic cement andsetting.

has taken place, peripheral. drain members; 8 may be saturated with waterby methods. explained in connection With;theimpregnationof the device of Figure 8 with a solution of. an oxygen supplying compound, water being. substituted for the solution. With respect to FigureS, the solvent obviously is, inpart at: least, transferred'tothe hydraulic cement; Also; itis; obviousthat after shaped passageways have been formed, as previously described, these maybe filledwith water to promote curing. Many hydraulic cements set over-a comparatively long period of time, some not reaching maximum strength for several weeks after being poured. During this period hydration isproceeding slowly and frequently water is required to accelerate and complete theprocess.

Many'modifications, fallingwithin the spirit and scope of the present invention, will occur to those skilled in the art to which it pertains. For example, while the-devices shown in Figures 1- to 8 have circular cross'sections, obviously, this isnot-a necessary requirement; Furthermore while the devices shown herein, for example, in- Figures 9 to 13, have uniform cross sections throughouttheirlength, this, too, is not a necessary requirement; If desired, thedevices of this invention maybe oftapering cross'section, as has been mentioned previously; Furthermore, it is within the purview-of this invention toprovide-enlargements at spaced intervals along= theburn. out device. Theseenlargements, are also.

capable of,self-sustained.combustion on ignition and after combustion leave enlargements at:

spaced intervals within the structure which may serve, for; example, as outlet boxes or receptacles for the-installation of outlet boxes and for. other. similar purposes. Such a modification is shown in Figure 13, wherein device I, at any desired point in its run, expands into the enlarged section. [6. The core of this enlarged section is also capable-of self-sustained combustion and is surrounded by a relatively or completely water'impervious sheath. If device I isprovided with, a-v

peripheral sheath of drain material as illustrated,

: for example, in Figures 6 and 7, then enlargement I5 is likewise provided witha peripheral sheath of drain material. It is not necessary that the enlargement l6 bean integral part of device I, as shownin Figure 13. If desired, a separate enlarged section l6 of any size and shape may be placed continguous todevice I at any point of its run. This modification is shown in Figure 14. During combustion of l, the immediately adjacent enlargement l 6 also ignites-and the combus- 5, tion thereof produces a cavity of any desired size or shape at any desired point along the path of I-.

While this invention has been described in connection with comparatively long runs of the devices of Figures 1 to 8, this is obviously not a necessary limitation. Short length of these devices may be used to make corresponding cavities which may be used to receive bolts which are grouted in as usual and then used for-the attachment of desired devicesv orstructures to the cement or concrete. Or the cavities, after formax through the short passageway and out the other. The resulting free ends of the wire, cable or the like'provide means forattaching exterior members to the construction member M.

Yet another mode of application of a short length of a modified form of device I is shown in Figure, 16. In this embodiment, device. I is provided with an integral, continuous helical rib I! along at least a portion of the longitudinal dimension thereof. The pitch and size of the rib l! are selected to conform to the pitch and depth of the thread on a bolt to be employed subsequently. After the burn out operation, it is obvious that a .cavity is formed in M having an internal thread that will engage the thread of the selected bolt which may be screwed into the cavity as usual and used as a point of attachment for devices or structures exterior to M. It is also apparentthat the contour of the device may vary to form cavities for receiving various types of brackets and other devices.

This invention has been described largely in connection with hydraulic cements, but this is notanecessary: limitation. Other'materials of construction maybe employed, in which case obvious modifications of the invention described may be desirable or necessary. For example, instead of being-applied to cement or concrete, cast or molded plastics may be employed. In such cases, obviously peripheral drain members are unnecessary and undesirable. Also, relativelyor completely water impervious sheaths are unnecessary. When this invention is applied to plastics, novel effects may be achieved in some instances by incorporating certain materials into the peripheral layer of device I, the nature of the material employed being governed by the plastic being used. Among such suitable materials may be mentioned trioxane or paraformaldehyde (urea-formaldehyde or phenol-formaldehyde resins), urea, melamine and catalytic agents such as peroxides, persulfates, acids and materials producing acidic fumes when heated. When employed in this modified form, shaped passageways can be formed in plastics which have a surface hardness appreciably above that exhibited by the plastic mass as a whole.

While in the preceding description device l was positioned and then surrounded with material in a plastic condition or was laid on a material in a plastic condition and then covered by additional plastic, this is not a necessary limitation. If desired, device I may be forced into a mass of material in plastic condition. For example, a length of device I may be laid upon the surface of a mass of plastic material and then forced into the body thereof by suitable forked bars. 01' device I may be weighted, either continuously along its length or at spaced intervals so that when placed upon the surface of a plastic material, such as plastic hydraulic cement or a plastic body of earthy nature, it will sink beneath the surface thereof.

Be it remembered that, while the present invention has been described in connection with specific details thereof, these are illustrative only and in no way limit the spirit and scope thereof except insofar as such specific details are incorporated in the appended claims.

We claim:

1. A duct forming member of the character described comprising, in combination, a peripheral water absorptive sheath surrounding a relatively water impervious sheath, said relatively water impervious sheath in turn surrounding a core capable of self-sustained combustion.

2. A duct forming member of the character described comprising, in combination, a peripheral water absorptive combustible sheath surrounding a relatively water impervious combustible sheath, said last named sheath surrounding a core capable of self-sustained combustion.

3. A duct forming member of the character described, comprising, in combination, a peripheral water absorptive sheath surrounding a relatively water impervious sheath, said relatively water impervious sheath in turn surrounding a core capable of self-sustained combustion, and a non-combustible element extending throughout the longitudinal dimension of said core.

4. A duct forming member of the character described comprising, in combination, a peripheral water absorptive sheath surrounding a relatively water impervious sheath, said relatively Water impervious sheath in turn surrounding a core capable of self-sustained combustion, and a train capable of self-sustained combustion extending throughout the longitudinal dimension of said core, said train and core being so constituted that the rate of combusion of said train will be greater than the rate of combusion of said core.

WARNER F. WILHELM. WARREN F. WILI-IELM.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 694,271 Harris et a1 Feb. 25, 1902 922,343 Schulman May 18, 1909 1,465,222 Kirton Aug. 14, 1923 1,593,831 King July 27, 1926 1,619,362 Murray Mar. 1, 1927 1,648,149 Reeve Nov. 8, 1927 1,767,586 Hudson June 24, 1930 1,956,575 Hinsky May 1, 1934 2,171,006 Morgan et a1 Aug. 29, 1939 2,239,051 Pearsall Apr. 22, 1941 

1. A DUCT FORMING MEMBER OF THE CHARACTER DESCRIBED COMPRISING, IN COMBINATION, A PERIPHERAL WATER ABSORPTIVE SHEATH SURROUNDING A RELATIVELY WATER IMPERVIOUS SHEATH, SAID RELATIVELY WATER IMPERVIOUS SHEATH IN TURN SURROUNDING A CORE CAPABLE OF SELF-SUSTAINED COMBUSTION. 